A
bstract
We present the first combination of NLO QCD matrix elements for di-Higgs production, retaining the full top quark mass dependence, with a parton shower. Results are provided within both the ...POWHEG-BOX and MadGraph5_aMC@NLO Monte Carlo frameworks. We assess in detail the theoretical uncertainties and provide differential results. We find that, as expected, the shower effects are relatively large for observables like the transverse momentum of the Higgs boson pair, which are sensitive to extra radiation. However, these shower effects are still much smaller than the differences between the Born-improved HEFT approximation and the full NLO calculation in the tails of the distributions.
A
bstract
We present results for Higgs boson pair production with variations of the trilinear Higgs boson self coupling at next-to-leading order (NLO) in QCD including the full top quark mass ...dependence. Differential results for the LHC at 14 TeV are presented and we discuss the implications of anomalous trilinear couplings as well as differences between the Pythia and Herwig parton showers in combination with POWHEG. The implementation of the NLO QCD calculation with variable Higgs boson self coupling is made publicly available in the POWHEG-BOX-V2 Monte Carlo framework. A simple method for using the new implementation to study also variations of the top quark Yukawa coupling is described.
We present the next-to-leading-order QCD corrections to the production of a Higgs boson in association with one jet at the LHC including the full top-quark mass dependence. The mass of the bottom ...quark is neglected. The two-loop integrals appearing in the virtual contribution are calculated numerically using the method of sector decomposition. We study the Higgs boson transverse momentum distribution, focusing on the high p_{t,H} region, where the top-quark loop is resolved. We find that the next-to-leading-order QCD corrections are large but that the ratio of the next-to-leading-order to leading-order result is similar to that obtained by computing in the limit of large top-quark mass.
We report on the calculation of the cross section for Higgs boson production in association with three jets via gluon fusion, at next-to-leading-order (NLO) accuracy in QCD, in the infinite top-mass ...approximation. After including the complete NLO QCD corrections, we observe a strong reduction in the scale dependence of the result, and an increased steepness in the transverse momentum distributions of both the Higgs boson and the leading jets. The results are obtained with the combined use of GOSAM, SHERPA, and the MADDIPOLE-MADEVENT framework.
Hadronisation effects in event-shape moments Gehrmann, T.; Jaquier, M.; Luisoni, G.
The European physical journal. C, Particles and fields,
05/2010, Letnik:
67, Številka:
1-2
Journal Article
Recenzirano
Odprti dostop
We study the moments of hadronic event shapes in
e
+
e
−
annihilation within the context of next-to-next-to-leading order (NNLO) perturbative QCD predictions combined with non-perturbative power ...corrections in the dispersive model. This model is extended to match the NNLO perturbative prediction. The resulting theoretical expression has been compared to experimental data from JADE and OPAL, and a new value for
α
s
(
M
Z
) has been determined, as well as of the average coupling
α
0
in the non-perturbative region below
μ
I
=2 GeV within the dispersive model:
The precision of the
α
s
(
M
Z
) value has been improved in comparison to the previously available next-to-leading order analysis. We observe that the resulting power corrections are considerably larger than those estimated from hadronisation models in multi-purpose event generator programs.
The couplings of the Higgs boson to other particles are increasingly well measured by the ATLAS and CMS experiments. The Higgs boson trilinear self-coupling however is still largely unconstrained, ...mainly due to the low cross-section for Higgs boson pair production. We present inclusive and differential results for the NLO QCD corrections to Higgs boson pair production with the full top-quark mass dependence, where the Higgs trilinear coupling is varied to non-SM values. The fixed-order calculation is supplemented by parton showering within the Powheg-BOX-V2 event generator, and both Pythia8 and Herwig7 parton-shower algorithms are implemented in a preliminary study of shower effects.
We present the calculation of the cross section for Higgs boson production in association with a top quark pair plus one jet, at next-to-leading-order accuracy in QCD. All mass dependence is retained ...without recurring to any approximation. After including the complete next-to-leading-order QCD corrections, we observe a strong reduction in the scale dependence of the result. We also show distributions for the invariant mass of the top quark pair, with and without the additional jet, and for the transverse momentum and the pseudorapidity of the Higgs boson. Results for the virtual contributions are obtained with a novel reduction approach based on integrand decomposition via the Laurent expansion, as implemented in the library, NINJA. Cross sections and differential distributions are obtained with an automated setup which combines the GOSAM and SHERPA frameworks.
We present an update of the Binoth Les Houches Accord (BLHA) to standardise the interface between Monte Carlo programs and codes providing one-loop matrix elements.
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